Add ChronicleMap.readKey() and readValue() for convenient work with BytesMapEventListener

src/main/java/net/openhft/chronicle/map/BytesMapEventListener.java

@@ -36,6 +36,9 @@ import java.io.Serializable;
  *     alignment (see {@link ChronicleMapBuilder#entryAndValueAlignment(Alignment)}
  *     ), followed by the serialized value itself.</li>
  * </ul>
+ *
+ * <p>There are helper methods {@link ChronicleMap#readKey(Bytes, long)} and
+ * {@link ChronicleMap#readValue(Bytes, long)} that help to deal with this.
  */
 public abstract class BytesMapEventListener implements Serializable {
     private static final long serialVersionUID = 0L;

src/main/java/net/openhft/chronicle/map/ChronicleMap.java

@@ -294,6 +294,10 @@ public interface ChronicleMap<K, V> extends ConcurrentMap<K, V>, ChronicleHash {
      */
     K newKeyInstance();
 
+    K readKey(Bytes entry, long keyPos);
+
+    V readValue(Bytes entry, long valuePos);
+
     /**
      * @return the class of {@code <K>}
      */

src/main/java/net/openhft/chronicle/map/StatelessChronicleMap.java

@@ -217,6 +217,16 @@ class StatelessChronicleMap<K, V> implements ChronicleMap<K, V>, Closeable, Clon
         return VanillaChronicleMap.newInstance(kClass, true);
     }
 
+    @Override
+    public K readKey(Bytes entry, long keyPos) {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public V readValue(Bytes entry, long valuePos) {
+        throw new UnsupportedOperationException();
+    }
+
     @Override
     public Class<K> keyClass() {
         return kClass;

src/main/java/net/openhft/chronicle/map/VanillaChronicleMap.java

@@ -233,6 +233,33 @@ class VanillaChronicleMap<K, KI, MKI extends MetaBytesInterop<K, ? super KI>,
         }
     }
 
+    @Override
+    public K readKey(Bytes entry, long keyPos) {
+        long initialPos = entry.position();
+        try {
+            entry.position(keyPos);
+            long keySize = keySizeMarshaller.readSize(entry);
+            ThreadLocalCopies copies = keyReaderProvider.getCopies(null);
+            return keyReaderProvider.get(copies, originalKeyReader).read(entry, keySize);
+        } finally {
+            entry.position(initialPos);
+        }
+    }
+
+    @Override
+    public V readValue(Bytes entry, long valuePos) {
+        long initialPos = entry.position();
+        try {
+            entry.position(valuePos);
+            long valueSize = valueSizeMarshaller.readSize(entry);
+            alignment.alignPositionAddr(entry);
+            ThreadLocalCopies copies = valueReaderProvider.getCopies(null);
+            return valueReaderProvider.get(copies, originalValueReader).read(entry, valueSize);
+        } finally {
+            entry.position(initialPos);
+        }
+    }
+
     static void segmentStateNotNullImpliesCopiesNotNull(
             @Nullable ThreadLocalCopies copies, @Nullable SegmentState segmentState) {
         assert copies != null || segmentState == null; // segmentState != null -> copies != null

src/test/java/net/openhft/chronicle/map/ReplicationCheckingMap.java

@@ -16,6 +16,7 @@
 
 package net.openhft.chronicle.map;
 
+import net.openhft.lang.io.Bytes;
 import org.jetbrains.annotations.NotNull;
 import org.junit.Assert;
 
@@ -245,6 +246,16 @@ public class ReplicationCheckingMap<K, V> implements ChronicleMap<K, V> {
         throw new UnsupportedOperationException();
     }
 
+    @Override
+    public K readKey(Bytes entry, long keyPos) {
+        return map1.readKey(entry, keyPos);
+    }
+
+    @Override
+    public V readValue(Bytes entry, long valuePos) {
+        return map1.readValue(entry, valuePos);
+    }
+
     @Override
     public Class<K> keyClass() {
         return map1.keyClass();

src/test/java/net/openhft/chronicle/map/jsr166/map/StatelessChronicleMapTest.java

@@ -19,6 +19,7 @@ package net.openhft.chronicle.map.jsr166.map;
 import net.openhft.chronicle.hash.replication.TcpTransportAndNetworkConfig;
 import net.openhft.chronicle.map.*;
 import net.openhft.chronicle.map.jsr166.JSR166TestCase;
+import net.openhft.lang.io.Bytes;
 import org.jetbrains.annotations.NotNull;
 import org.junit.After;
 import org.junit.Before;
@@ -198,6 +199,16 @@ public class StatelessChronicleMapTest extends JSR166TestCase {
             throw new UnsupportedOperationException();
         }
 
+        @Override
+        public K readKey(Bytes entry, long keyPos) {
+            return d.readKey(entry, keyPos);
+        }
+
+        @Override
+        public V readValue(Bytes entry, long valuePos) {
+            return d.readValue(entry, valuePos);
+        }
+
         @Override
         public Class<K> keyClass() {
             return d.keyClass();